Behavior of tomato plants genetically manipulated to have a lower level of ethylene

Abstract

Compartmentalization of enzymes involved in ethylene synthesis plays an important role in a plant's response to flooding and other stresses. Heterologous gene expression, plant growth-promoting bacteria with ACC deaminase activity and selective inhibitors were used to ameliorate the effects of stress ethylene. In this study, the upstream region of the Enterobacter cloacae UW4 ACC deaminase gene was found to contain FNR-, CRP- and LRP-binding sites and an novel LRP-like protein named Bacca that appear to be involved in the transcriptional regulation of the acd gene. To determine the effect of ACC deaminase activity on the phenotype of tomato plant, transgenic plants were compared to non-transformed plants in a number of traits including root and shoot growth, leaf chlorophyll content, fruit weight, lycopene and B-carotene content, and the effect of AG+. The acd gene was under the transcriptional control of either the 35S cauliflower mosaic virus promoter, the rolD promoter from Agrobacterium rhizogenes or the PRB-1b promoter from tobacco. The 35S and rolD plants behaved similarly to one another and differently from the non-transformed plants. Transgenic tomato plants were also compared to the non-transformed plants in the ability to accumulate Cd, Co, Cu, Mg, Ni, Pb, or Zn. Parameters that were studied include metal concentration, ACC deaminase activity, root and shoot growth, and leaf chlorophyll content. Transgenic tomato plants acquired a greater amount of metals and were less affected by the metals that were non-transformed plants. Both transgenic tomato plants and plants grown from seeds bacterized with bacteria expressing ACC deaminase were compared to non-transformed plants in their response to flooding based on the shoot height, fresh and dry weight, epinasty, ACC deaminase activity, ethylene production, and chlorophyll and protein content. All of the transgenic tomato plants as well as the bacterized plants showed a significantly increased tolerance to flooding stress.